Sonar systems are typically installed in defence vessels for surveillance purposes and more particularly for detecting the presence of submarines. These known sonar systems include towed array sonar deployed from surface vessels such as frigates. The towed array sonar includes a system of hydrophones towed behind the frigate or other surface vessel via a tow cable. The tow cable can be up to one or more kilometres in length and is spooled about a cable drum mounted on the deck or alongside the hull of the surface vessel from which it is deployed and retrieved.